1. Field of the Invention
This invention relates to a copper-based high-temperature superconducting material in which the critical current density (Jc) and irreversible field (Hirr) are improved without a major decrease in the high superconducting transition temperature (Tc).
2. Description of the Prior Art
In conventional superconductors having a layered structure such as, for example, Y, Bi, Tl, and Hg based copper-oxide superconductors, as shown in FIG. 2, because overdoping was used to produce a major decrease in the Tc, even if the superconducting anisotropy .gamma. .gamma. being the coherence length ratio, defined as .xi.ab/.xi.c) was decreased, in overall terms there was no improvement in the superconducting characteristics. As a result, at 77 K, it has not been possible to achieve a high Jc and a high Hirr under a high magnetic field condition, which made it difficult to practically apply the superconducting material as wire, in bulk form or as a device material.
With previous high-temperature superconductors having a layered structure, it was difficult to adequately increase the carrier concentration and maintain a high Tc in the overdoped region with the somewhat increased carrier concentration, particularly impossible to achieve a high Jc and a high Hirr under a high magnetic field condition, posing problems with respect to the practical use of the superconducting material as wire, in bulk form or as a device material.
Thus, an object of the present invention is to provide an overdoped high-temperature superconducting material having a high superconducting transition temperature Tc, a high critical current density Jc and a high irreversible field Hirr.